1. Field of the Invention
The present invention relates, in general, to apparatuses for moving headrests and, more particularly, to an apparatus for moving a headrest which is assembled in such a way that a rotating cam is provided on a stay rod after passing through one end of the stay rod and a bending part thereof.
2. Description of the Related Art
A conventional headrest includes a stay rod 100, a braking cam 200, a movable cam 300, a return spring 400, a support spring 500, a rotating member 600 and a release rod 700. The stay rod 100 includes a horizontal part 101 and vertical parts 102 which extend downwards from opposite ends of the horizontal part 101. The braking cam 200 has a shaft hole 20a in a central portion thereof so that the braking cam 200 is fitted over the horizontal part 101 through the shaft hole 20a. At least one braking depression 201 and at least one braking protrusion 202 are provided on one axial side surface of the braking cam 200. The movable cam 300 has a shaft hole 30a in a central portion thereof. Thus, the movable cam 300 is fitted over the horizontal part through the shaft hole 30a such that the movable cam 300 is brought into contact with the braking cam 200. At least one locking protrusion 301 and at least one locking depression 302 which engage with the braking depression 201 and the braking protrusion 202 are formed in a corresponding axial side surface of the movable cam 300. A coupling piece 303 which has a coupling hole 304 extends outward from an upper portion of a circumferential outer surface of the movable cam 300. The return spring 400 is provided on the horizontal part 101 and disposed outside the braking cam 200. An inner end 401 of the return spring 400 is locked to the braking cam 200. The support spring 500 is provided on the horizontal part 101 and disposed outside the movable cam 300. The elastic force of the support spring 500 biases the movable cam 300 to the braking cam 200. The rotating member 600 includes a pair of side plates 602 and 602′ which are provided on the horizontal part 101 and are respectively disposed on outer ends of the return spring 400 and support spring 500. A shaft hole 60a is formed in each side plate 602, 602′. A front surface plate 601 laterally extends inward from a front end of each side plate 602, 602′. The front surface plates 601 of the side plates 602 and 602′ are overlapped with each other and adhered to each other. A hook hole 603 is formed in an upper portion of the first side plate 602, and an outer end of the return spring 400 is hooked to the hook hole 603. Thus, the rotating member 600 is biased rearward by the elastic force of the return spring 400 so that the rotating member 600 can be rotated rearward and oriented horizontally. The release rod 700 has an inner end part 70a which is formed between a stepped portion 701 and an inner end of the release rod 700. The diameter of the inner end part 70a is less than that of the other portion of the release rod 700. The inner end part 70a is inserted into the coupling hole 304 of the coupling piece 303 and a support hole 605 of the second side plate 602′ which have the same diameter as that of the inner end part 70a. A button 702 is coupled to an outer end of the release rod 700 which passes through the through hole 604 of the first side plate 602, an inner cover and a side surface of a support member. The outer end of the release rod 700 is exposed to the outside of a vehicle seat.
In the conventional vehicle headrest having the above-mentioned construction, when the support member is rotated upright, the rotating member 600 is also rotated upright. At this time, the movable cam 300 which is coupled to the rotating member 600 by the inner end part 70a of the release rod 700 is also rotated upright.
Then, the locking protrusion 301 and the locking depression 302 of the movable cam 300 respectively face the braking depression 201 and the braking protrusion 202 of the braking cam 200. Simultaneously, the movable cam 300 is pushed onto the braking cam 200 by the elastic force of the support spring 500 so that the locking protrusion 301 and the braking protrusion 202 respectively engage with the braking depression 201 and the locking depression 302. Thereby, the movable cam 300 and the rotating member 600 are restricted from rotating. As a result, the support member is maintained in the upright state without rotating rearward, even though the elastic force of the return spring 400 is applied thereto.
Furthermore, when the rotating member 600 is in the upright state, a lower end of the front surface plate 601 is supported on a rear support piece 204 of the braking cam 200. Thus, even if comparatively strong impact is applied thereto in the forward direction, the rotating member 600 is maintained in the upright state without rotating forward.
Meanwhile, to rotate the support member downward, the button 702 is pushed so that the release rod 700 is moved inward. Then, the movable cam 300 is moved along with the release rod 700 and separated from the braking cam 200. Thereby, the locking protrusion 301 and the locking depression 302 of the movable cam 300 are removed from the braking depression 201 and the braking protrusion 202 of the braking cam 200. The rotating member 600 is thus released from the brake state and immediately rotated rearward by the elastic force of the return spring 400. Eventually, the support member is rotated downward so that it can be prevented from blocking the view.
As such, when the support member has rotated downward, the locking protrusion 301 of the movable cam 300 that has rotated rearward along with the rotating member 600 is misaligned from the braking depression 201 of the braking cam 200 while the braking protrusion 202 is misaligned from the locking depression 302. In addition, the locking protrusion 301 and the braking protrusion 202 become supported on planar portions of corresponding support parts. Therefore, even though the movable cam 300 is pushed toward the braking cam by the elastic force of the support spring 500, the locking protrusion 301 and the braking protrusion 202 do not engage with the braking depression 201 and the locking depression 302.
In this state, if the support member is rotated forward such that it is oriented upright, the movable cam 300 is rotated forward, and the locking protrusion 301 and the braking protrusion 202 are moved from the planar portions of the support parts along curved portions of the support parts. When the locking protrusion 301 and the braking protrusion 202 respectively reach the braking depression 201 and the locking depression 302, the locking protrusion 301 and the braking protrusion 202 can no longer be supported by the support parts. Then, the movable cam 300 is immediately pushed onto the braking cam 200 by the elastic force of the support spring 500, so that the locking protrusion 301 and the braking protrusion 202 are respectively inserted into the braking depression 201 and the locking depression 302. Thereby, the movable cam 300 is rotated neither forward nor rearward and is maintained in the upright state.
Here, each planar portion of the support parts is lower than the braking protrusion 202 or the locking protrusion 301. Each curved portion is higher than the planar portion but is lower than the braking protrusion 202 or the locking protrusion 301. Therefore, in the process of rotating the movable cam 300 forward and orienting it upright, when the locking protrusion 301 and the braking protrusion 202 which have been disposed on the planar portions of the support parts reach the braking depression 201 and the locking depression 302 after passing over the curved portions, because the curved portions are lower than the locking protrusion 301 and the braking protrusion 202 which are adjacent to the corresponding braking depression 201 and locking depression 302, this height difference makes the end of the locking protrusion 301 be supported by the end of the braking protrusion 201. Thereby, the movable cam 300 is stopped and can no longer be rotated. Simultaneously, the movable cam 300 is pushed onto the braking cam 200 by the elastic force of the support spring 500 so that the locking protrusion 301 and the braking protrusion 202 can reliably engage with the braking depression 201 and the locking depression 302.
When the movable cam 300 is rotated downward, the locking protrusion 301 and the braking protrusion 202 are supported on the planar portions of the corresponding support parts. At this time, because of a difference in height between the planar portions and the locking protrusion 301 and braking protrusion 202, a stop portion is formed on each side surface of the locking protrusion 301 and braking protrusion 202 which come into contact with the corresponding planar portions. Then, the stop portions of the locking protrusion 301 and braking protrusion 202 that are placed on the planar portions are respectively blocked by the corresponding stop portions of the braking protrusion 202 and locking protrusion 301. Thereby, the movable cam 300 no long rotates downward.
In the drawing, the reference numeral 800 denotes a coupling cap, and 801 denotes a coupling part.
However, in the conventional headrest, to couple the two opposite parts of the rotating member 600 to the stay rod 100, work such as welding is required. In addition, the two opposite parts of the rotating member 600 must also be coupled to each other by welding or the like after the movable cam 300 and the braking cam 200 have been disposed between the two opposite parts. Therefore, the assembly process is complicated, and the production cost is also increased.